Method of producing propylene oxide,propyleneglycol and its esters

ABSTRACT

Propylene oxide, propylene glycol and esters thereof are produced by oxidizing propylene with an oxygen containing gas in an inert solvent at a temperature of at least 120* C. and a pressure of 50 to 10 atm in the presence of fluorine containing catalysts.

mted States atent 1151 3,674,813

Bljumberg et al. July 4, 1972 {54] METHOD OF PRODUCING PROPYLENE 58Field of Search ..260/348.5 LV, 635

OXIDE, PROPYLENEGLYCOL AND ITS [56] References Cited [72] Inventors:Erna Albertovna Bljumberg, Leninsky UNITED STATES PATENTS Prospekt,Alexandr vasilievich 2,784,202 3/1957 Gardner et a] ..260/348.5 B l v, Ly p p 3,222,382 12/1965 Lanthier ..260/348.5 Svetlana Pavlovna B l v Lninky 3,238,229 3/1966 Reid ..260/348.5 prospekt, 30, kv. 104; NikolaiMarkovich 2,530,509 11/1950 Cook ..260/348.5 Emanuel, Vorobievskoeshosse, 26, kv. 4 a" f Moscow FOREIGN PATENTS OR APPLlCATlONS 22 Filed;June 19 19 7 872,560 7/196] Great Britain ..260/348.5

[ PP NOJ 647,250 Primary Examiner-Norma S. Milestone Attorney-Waters,Roditi, Schwartz & Nissen [30] Foreign Appllcatlon Priority Data [57]ABSTRACT g8 Propylene oxide, propylene glycol and esters thereof areproduced by oxidizing propylene with an oxygen containing gas in aninert solvent at a temperature of at least 120 C. and [52] US. Cl..260/348.5, 260/488, 260/533, a pressure of 50 to 10 mm in the presenceof fluorine coma,

260/597, 260/601, 260/632, 260/635 mg catalysts [51] Int. Cl ..C07d1/12, C07d 1/08, C07d 31/20,

C07d 27/ l 2 8 Claims, No Drawings METHOD OF PRODUCING PROPYLENE OXIDE,PROPYLENEGLYCOL AND ITS ESTERS This invention relates to methods ofproducing propylene oxide, propyleneglycol and esters. Propylene oxideis a preferred starting material for production of polymers,propyleneglycol, de-emulsifiers, for glycerin synthesis, and for otheruses in the chemical industry.

Until now, the chlorohydrin method has been practically the only oneused in industry for propylene oxide production. According to thismethod, 3 tons of chlorine and alkali subsequently converted tonon-utilizable waste polluting the environmental nature are consumed per1 ton of the product obtained.

There are also known methods for the chlorine free production ofpropylene oxide by liquid-phase oxidation of propylene. These methodsinvolve propylene oxidation in inert solvents at temperatures of 150 to200 C and pressures of 50 to 250 atm, epoxidation of propylene withvarious reagents such as peracetic acid solutions, ethylbenzenehydroperoxide in the presence of catalysts, and oxidation of propylenein conjunction with other organic compounds (aldehydes, ketones,hydrocarbons) which undergo oxidation more readily than the said olefin.

Until now, propylene oxidation in inert solvents (mainly in benzene) hasnot been realized in industry due to the low concentration of propyleneoxide in the reacting mixture (amounting to not more than 2.0 weightpercent), low selectivity of propylene oxide and propyleneglycolformation, great amount of side products, and considerable conversion ofpropylene to carbon dioxide. Moreover, this process may be conductedonly to a small extent of propylene conversion, not exceeding 10 molarpercent, for at higher conversion, CO becomes the main product ofpropylene oxidation.

Improvements of the process by use of various catalysts, by rapidremoval of acids from the reaction mixture in order to prevent theirreactions with propylene oxide, etc. (U.S. Pats. Nos. 2,784,202, 1957;3,071,601, 1963; 3,153,058, 1964; British Pat. No. 917,926, 1959) failedto secure an efficient technological process.

One of the reasons for the low yields of useful products in propyleneoxidation is the undesirable effect of the reactor material (stainlesssteel) on the mechanism of the process. As stated in a paper by EA.Bljumberg, Ju.D. Norikov and N.M.Emanuel published in Dokl. Akad. NaukSSSR vol. 151, No.5 page 1,129, 1963, stainless steel used inliquid-phase butane oxidation leads to isomerization and decompositionof peroxy radicals, yielding products which contain less than fourcarbon atoms.

The object of the present invention is to eliminate the abovedisadvantages of the known process of propylene oxidation in a benzenesolution and to obtain an effective method for the industrial productionof propylene oxide and of propyleneglycol, based on the cited reaction.

On the basis of the above theoretical concepts concerning theundesirable catalyzing effect of stainless steel, applicants proposethat the process of propylene oxidation in inert solvents, be conductedin non-metallic reactors, particularly those which do not induceisomerization and decomposition of peroxy radicals.

The effect of stainless steel upon the liquid-phase oxidation ofhydrocarbons shows that heterogeneous catalysis takes place in thesereactions, thus causing a search for positive heterogeneous catalystsmaking for an increase in the reaction selectivity.

in the present invention fluorine-containing compounds, for example,fluorine-containing polymers such as Teflon (polytetrafluoroethylene)and fluorine-containing salts, are used as catalysts.

The invention is a method of producing propylene oxide, propyleneglycoland its esters comprising oxiding propylene in an inert solvent with anoxygen-containing gas at a temperature of at least 120 C, a pressure of50 to 100 atm in a nonmetallic reactor and in the presence of afluorine-containing catalyst.

Glass or porcelain, enamel may be used as the non-metallic materials.Teflon (polytetrafluoroethylene), salts of alkaline earth and alkalimetals such as KgSiFg, NaF, KJaF etc., may serve as thefluorine-containing catalysts.

Benzene, acetone and other compounds which do not oxidize or oxidizeonly weakly under the conditions described above may be used as inertsolvents.

The efficiency of the process according to the present invention is setforth in detail in the following non-limiting examples.

EXAMPLE 1 A Teflon reactor in a steel casing is charged with 50 ml ofbenzene, the reactor is hermetized, air from a tank is fed through aTeflon tube to a pressure of 50 atrn. The reactor is heated to C and 30ml of liquid propylene are introduced under air pressure. Air is thenbubbled through the mixture. Steady-state concentration of propylenedissolved in benzene is ensured by continuous prernixing of propylene tothe stream of air fed to the reactor.

Samples are withdrawn in the course of propylene oxidation. These areanalyzed by means of chemical techniques and of gas-liquidchromatography using a flame ionization detector. Propyleneglycoldistearate (15 weight percent of the celite used) represent the immobilephase. The acids are analyzed by means of a chromatograph with akatharometer. In this case, the immobile liquid phase is a mixture of 5percent of silicon oil, 5 percent of paraffin, 20 percent ofdioctylsebacinate and 10 percent of stearic acid.

The distribution of reaction products and their yields per reactedpropylene are shown in Table 1. The same Table lists the results ofexperiments made under the abovementioned conditions but using reactorsof stainless steel (with no wall coating) and of glass.

The distribution of products for all reactors refers to the timecorresponding to maximum propylene oxide concentration in the reactingmixture.

TABLE 1 Reaction Stainless product steel Glass Teflon 1n moln moin molarlar lar perperpercent cent cent In of re- In of re- In of reweight actedweight acted weight acted P P PY' D l P py- P P PY cent lene cent lenecent lene Propylene oxide 1.1 52.0 4.8 46.5 7.5 33.0 propyleneglycol andits esters 1.3 10.5 13.6 47.2 acetic acid 0.7 2.0 2.9 15.9 3.4 8.5formic acid 0.6 1.5 2.2 7.4 2.0 3.9 acetaldehyde 0.4 5.6 0.22 1.0 0.41.2 acetone 0.7 14.5 0.30 3.0 0.3 1.6 isopropyl alcohol 0.10 1.0 0.2 1.1Methylacetate 0.2 0.5 allyl alcohol 0.30 3.2 acrolein 0.08 0.5 acrylicacid 0.2 1.2 methanol 0.15 1.0 0.1 0.3 methylformiate 1.4 8.2 0.6 2.0carbon dioxide 24.4 0.6 0.7 Total: 100.0 100.0 100.0 Extent of propyleneconversion, in molar percent 10.0 22.9 49.0

EXAMPLE 2 The experiment is carried out as in Example 1, in a glassreactor operating under bilateral pressure of 50 atm. The glass reactoris made as a long tube cased in a steel autoclave. The lower (broader)part of the reactor is heated by an electric furnace and serves as thereaction zone. The upper part acts as a reflux condenser, thuspreventing contact between the reacting mixture and metal. Thedistribution of propylene oxidation products is shown in Table 1.

EXAMPLE 3 The experiment is carried out as in Example 1, in a Teflonreactor filled with Teflon chips. The reactor is charged with 50 ml ofbenzene. In 8 hours after the start of oxidation the overall content ofthe reactor amounts to 140 ml. Amarked separation of the reactingmixture to two layers, that of the benzene solution (115 ml) and that ofthe aqueous solution (25 ml) is observed. The composition of both layersand the product yields per reacted propylene are shown in Table 2.

The experiment is carried out as in Example 1, but in a stainless steelreactor containing Teflon chips as heterogeneous catalyst.

The maximum concentration of propylene oxide (1.0 mole/l) is attained in3 hours after the start of the reaction. The distribution of productsand their yields per reacted propylene obtained to this time are shownin Table 3. The extent of propylene conversion during 3 hours of thereaction is 32 percent.

TABLE 3 Reaction Concentration Yield per reacted propylene, Molar per-Weight permolar percent cent cent Propylene oxide l.00 6.6 50.0Propyleneglycol and its esters 0.20 3.3 20.0 Acetic acid 0.28 1.9 9.5Formic acid 0.23 1.2 4.0 Acetone 0.04 0.26 2.0 lsopropyl alcohol 0.040.27 2.0 Acetaldehyde 0.08 0.40 2.5 CO, 0.05 10.00

Total: 100.00

EXAMPLE 5 A reactor of molybdenum glass is charged with 50 ml of benzeneand 1 g of K SiF The reactor is hermetized and air is admitted to apressure of 50 atm. The reactor is heated to C and 50 ml of liquidpropylene are introduced under air pressure. Air is then bubbled throughthe mixture. Steady-state concentration of the propylene dissolved inbenzene is ensured by continuous premixing of propylene to the stream ofair fed to the reactor. In 3 hours, a propylene oxide concentration inthe reacting mixture of 1.8 g weight percent is attained.

EXAMPLE 6 The experiment is carried out as in Example 5, with theexception that acetone is used as solvent. The reactor is charged with50 ml of acetone, 1 g of K SiF and 50 ml of propylene. The resultsobtained are shown in Table 4. The composition of products and theiryields per reacted propylene, as shown in this table, refer to the timecorresponding to maximum propylene oxide concentration.

EXAMPLE 7 The experiment is carried out as in Example 6, with theexception that 1 g of NaF is used as the fluorine-containing catalyst.The results obtained are shown in Table 4.

TABLE 4 Distribution of products and their yields in the liquid-phaseoxidation of propylene in an acetone solution in the presence offluorine-containing salts (referred to the time corresponding to maximumpropylene oxide concentration). A glass reactor; temperature of 145 C,pressure of 50 atm.

Reaction KgslFn NaF KJaF,

product Wt. Molar Wt. molar Wt. Molar percent percent of reof reofreacted acted acted p py P Pyp pylene lene lene Propylene oxide 9.4 44.06.0 33.0 4.9 29.0

Propyleneglycol 4.9 17.5 3.7 16.0 1.7 7.8

Propyleneglycol esters 3.7 6.8 4.7 10.2 2.1 4.7

Propylene oxide propyleneglycol estersl8.0 69.0 14.4 60.0 8.7 41.5

Acetic acid 3.4 10.3 2.0 9.5 2.9 9.0

Formic acid 1.7 3.6 6.1 13.0 4.4 17.0

Methylformiate 0.6 2.07 0.06 2.8 5.5 21.0

lsopropyl alcohol 0.7 3.06 0.05 2.3 1.1 6.4

Allyl alcohol 0.5 2.06 0.5 3.2 0.3 1.7

Carbon dioxide 11.0 12.0 11.0

Time corresponding to maximum concentration of propylene oxide 6.0 hrs3.0 hrs 4.0 hrs Extent of propylene conversion (molar percent of theoriginal propylene) 67.0 57.0 56.0

EXAMPLE 8 The experiment is carried out as in Example 6 and 7, l g of KTaF being used as catalyst. The results obtained are shown in Table 4.

EXAMPLE 9 TABLE 5 Reaction Concentration reacted propylene, product inacetone, molar per cent weight percent Propylene oxide5.5Propyleneglycol3.3 Propyleneglycol esters3.l Propylene oxidepropyleneglycol esters l 1.9 3 Acetic acid3.2 Formic acid4.9Methylformiate l .l lsopropyl alcohol 3.1 l Allyl alcohol2.5 l Carbondioxide- 1 We claim:

l. A method of producing propylene oxide, propyleneglycol and itsesters, which comprises oxidizing propylene with an oxygen-containinggas in an inert solvent selected from the group consisting of benzeneand acetone, at a temperature of at least 120 C and a pressure of 50 toatm in the presence of fluorine-containing catalyst selected from thegroup consisting of polytetrafluoroethylene, and fluorine salts ofalkali and alkaline earth metals.

2. A method according to claim 1, wherein the catalyst is K SiF 3. Amethod according to claim 1, wherein the catalyst is NaF.

4. A method according to claim 1, wherein the catalyst is K TaF 5. Aprocess for producing propylene oxide by direct oxidation whichcomprises dissolving propylene in an inert solvent selected from thegroup consisting of benzene and acetone and effecting oxidation at atemperature of at least C by feeding into the solution anoxygen-containing gas maintained at a pressure of from 50 atm to 100atm, wherein the reaction mixture consisting of propylene and oxygendissolved in said solvent is contacted with a fluorine-containing saltof a metal selected from the group consisting of alkali and alkalineearth metals.

6. A process according to claim 5, wherein the fluorine-containing saltis K SiF NaF or K TaF 7. A method according to claim 1 wherein thetemperature is 120 to C.

8. A process according to claim 5 wherein the temperature is 120 to 145C.

2. A method according to claim 1, wherein the catalyst is K2SiF6.
 3. Amethod according to claim 1, wherein the catalyst is NaF.
 4. A methodaccording to claim 1, wherein the catalyst is K2TaF7.
 5. A process forproducing propylene oxide by direct oxidation which comprises dissolvingpropylene in an inert solvent selected from the group consisting ofbenzene and acetone and effecting oxidation at a temperature of at least120* C by feeding into the solution an oxygen-containing gas maintainedat a pressure of from 50 atm to 100 atm, wherein the reaction mixtureconsisting of propylene and oxygen dissolved in said solvent iscontacted with a fluorine-containing salt of a metal selected from thegroup consisting of alkali and alkaline earth metals.
 6. A processaccording to claim 5, wherein the fluorine-containing salt is K2SiF6,NaF or K2TaF7.
 7. A method according to claim 1 wherein the temperatureis 120* to 145* C.
 8. A process according to claim 5 wherein thetemperature is 120* to 145* C.